In fiber optic telecommunications systems, it is common for optical fibers of transmission cables to be split into multiple strands, either by optical splitting of a signal carried by a single stranded cable or by fanning out the individual fibers of a multi-strand cable. Further, when such systems are installed, it is known to provide excess capacity in the installations to support future growth and utilization of the fibers. Often in these installations, modules including splitters or fanouts are used to provide the connection between transmission fibers and customer fibers. To reduce the cost and complexity of the initial installation and still provide options for future expansion, a module mounting chassis capable of mounting multiple modules may be used in such an installation.
While a chassis may accept several modules, the initial installation may only include fewer modules mounted in the chassis, or enough to serve current needs. These chassis may be configured with limited access to one or more sides, or may be mounted in cramped locations. In addition, some of these chassis may be pre-configured with the maximum capacity of transmission cables to accommodate and link to modules which may be installed in the future. Since it is desirable to have access to components within the chassis for cleaning during the installation of a new module, some provision or feature of the chassis will desirably permit a user to access and clean the connectors of these pre-connectorized and pre-installed transmission cables.
It is also desirable for the chassis to be configured to ensure that modules are installed correctly and aligned with other components within the chassis to mate with the pre-connectorized and pre-installed transmission cables.
In fiber-optic communications, it is also common for optical signals of transmission cables to be multiplexed. Wavelength division multiplexing (WDM) is a technology which multiplexes multiple optical carrier signals on a single optical fiber by using different wavelengths of laser light to carry different signals. This allows for a multiplication in capacity, in addition to making it possible to perform bidirectional communications over one strand of fiber.
A WDM system uses a multiplexer at the transmitter to join signals together and a demultiplexer at the receiver to split them apart. With the right type of fiber, it is possible to have a device that does both simultaneously, and can function as an optical add-drop multiplexer. WDM systems allow expansion of the capacity of the network without laying more fiber.
WDM systems are divided in different wavelength patterns: 1) conventional WDM; 2) dense WDM (DWDM); and 3) coarse WDM (CWDM). WDM, DWDM and CWDM are based on the same concept of using multiple wavelengths of light on a single fiber, but differ in the spacing of the wavelengths, number of channels, and the ability to amplify the multiplexed signals in the optical space.
In certain telecommunications applications, it might be desirable to combine wavelength division multiplexing technology with fiber optic signal splitting technology.